Technical Field
This disclosure relates to catheter obstructions.
Description of Related Art
Hydrocephalus is a condition characterized by excessive accumulation of cerebrospinal fluid (CSF) in the brain and a corresponding increase in intracranial pressure (ICP)
Hydrocephalus has been treated using implanted CSF shunts. CSF shunts can restore hydrodynamic balance by increasing CSF outflow to normalize ICP and improve symptoms. 70-80% patients with shunts improve postoperatively.
A shunt can include a ventricular (proximal) catheter, a valve mechanism, and a distal catheter. Peritoneum placement of the distal catheter is common, with other locations including the pleura, ureter, bladder, and vascular spaces.
Various shunts have been introduced, but can create complications due to inadequate shunt performance, such as obstruction of a catheter used in the shunt.
Implanted and external sensors exist to dynamically measure shunt flow [M. Geiger and L. Speckman, “Cerebral spinal fluid flow sensing device,” US 20060020239, 2006; S. Kassem, “Wireless flow sensor,” US 20130245403 A1, 2013; M. Swoboda, et al. “CSF shunt flow enhancer, method for generating CSF flow in shunts and assessment of partial and complete occlusion of CSF shunt systems,” US 20130102951 A1, 2013; M. Swoboda, et al. “Real time flow measurement system & method/’ US 20130109998 A1, 2013] and pressure [E. R. Cosman, “Telemetric differential pressure sensor with the improvement of a conductive shorted loop tuning element and a resonant circuit,” U.S. Pat. No. 4,593,703 A, 1986; E. R. Cosman, “Telemetric in-vivo calibration method and apparatus using a negative pressure applicator,” U.S. Pat. No. 4,676,255 A, 1987; M. N. Ericson, et al., “Implantable device for in-vivo intracranial and cerebrospinal fluid pressure monitoring,” U.S. Pat. No. 6,533,733 B1, 2003; A. Ginggen and Y. Tandy, “Combined pressure and flow sensor integrated in a shunt system,” US 20090204019 A1, 2009; K. Hughes and A. Strachan, “Sensor, circuitry, and method for wireless intracranial pressure monitoring,” US 20120265028 A1, 2013; I. Igarashi et al. “Intracranial pressure transducer,” U.S. Pat. No. 4,246,908 A, 1981; S. Kassem, “Wireless shunts with storage,” U.S. Pat. No. 8,480,612 B2, 2009; K. A. Miesel and L. Stylos, “Intracranial monitoring and therapy delivery control device, system and method,” U.S. Pat. No. 6,248,080 B1, 2001; C. B. Southworth, “Inflatable pressure indicator,” U.S. Pat. No. 5,935,084 A, 1999; M. Swoboda, et al., “Implantable pressure sensor,” US 20130247644 A1, 2013; G. A. Thomas, et al., “No clog shunt using a compact fluid drag path,” U.S. Pat. No. 8,088,091 B2, 2012; J. G. Venegas, “Apparatus and method for the detection of IV catheter obstruction and extravasation,” U.S. Pat. No. 5,026,348 A, 1991]. However, catheter obstruction may need to be inferred based on observed patterns of flow or pressure. This may be inefficient and can lead to false positives or negatives, as these measures are not direct measurements of patency.
Optical methods have been used to monitor movement of specific particles within CSF through fluidic channels. These optical methods provide feedback on applying a stimulus pulse between electrodes oriented in a similar design as this disclosed technology. [R. G. Dacey, et al., “Systems, devices, and methods including infection-fighting and monitoring shunts,” WO 2010098868 A1, 2010.]
Another approach involves measurement of electrochemical impedance within a hydrocephalic shunt environment as an indirect means of inferring volume of the CSF within the ventricles, which can be more accurate for determining CSF dynamics than pressure or flow [A. Linninger, “Monitoring and controlling hydrocephalus,” U.S. Pat. No. 8,457,733 B2, 2010]. However, this sensor system may not detect obstruction events of the catheter and instead may be used only to diagnose hydrocephalus.
Commercial sensor systems are being developed by Integra LifeSciences (Integra Camino), Transonic Systems, Aesculap (Meithke), and Issys. However, these sensors may use transduction principles and single time point measurements that provide a snapshot of CSF dynamics. However, they may not have the capability for multiple measurements over time, which is necessary to monitor progressive obstruction. Some may also monitor flow indirectly and may not provide quantitative measurement of patency or obstruction.